OLED (Organic Light Emitting Diode) features self-luminescence, slimness, fast response, wide visual angle, high resolution, high illumination, applicability to flexible displays, and adaptability to a wide range of temperature. Therefore, it is regarded as the new-generation display device to replace TFT-LCD (Thin Film Transistor Liquid Crystal Display). In OLED, the recombination of electrons and holes in the light emitting layer generates energy to excite the light emitting molecules from the ground state to the excited state. When the electrons back from the excited state to the ground state, excess energy is released in form of light waves. Thereby are obtained light emitting elements with different wavelengths.
So far, many patents have been proposed to improve the luminous efficiency of the light emitting layer of OLED. A R.O.C. patent No. I236174 disclosed an organic-inorganic light emitting diode structure, which comprises a substrate, a first electrode on the substrate, an organic-inorganic light emitting layer on the first electrode, and a second electrode on the organic-inorganic light emitting layer. The organic-inorganic light emitting layer contains a plurality of organic-inorganic composite quantum dots dispersed in a high polymer. Each organic-inorganic composite quantum dot includes a ZnX quantum dot and an organic molecule coating the surface of the quantum dot, wherein X is selected from a group consisting of S, Se, Te, and a combination thereof.
A R.O.C. patent No. 520612 disclosed an organic light emitting device, which comprises a substrate, an anodic electrode and a cathodic electrode on the substrate, and a light emitting layer between the anodic electrode and the cathodic electrode. The light emitting layer includes a primary agent and at least one blending agent. The primary agent contains an organic solid-state material having at least two compounds. The first compound is essentially non-polarity and able to transmit electrons and holes. The second compound is an organic compound having polarity greater than the first compound. The blending agent is selected from a material able to emit light from the light emitting device.
From the above description, it is known that promoting the luminous efficiency of OLED is an important subject in the field. Nevertheless, how to achieve the high luminous efficiency at the lower cost is still a challenge for the researchers.